Superior Vena Cava Syndrome

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Superior vena cava syndrome (SVCS) was traditionally considered an oncologic emergency, but only rarely does it present as a truly life-threatening emergency. This condition typically develops over days to weeks, with subtle symptoms at an early stage. Nurses can play a critical role in picking up these symptoms if they know who is at risk and how it presents.

Incidence and Etiology

SVCS was first described in 1757 by Dr. William Hunter in a patient with syphilitic aortic aneurysm. Since the mid-20 th century, malignancies have accounted for the large majority (at least 85%) of SVCS cases. Lung cancers are the most frequent cause, accounting for 85% of cases, with specifically small cell lung cancers implicated in 65% of cases (despite only representing 15-20% of all new lung cancers). This is most likely because small cell lung cancer has a tendency to form in the central part of the lungs, as well as a high rate of mediastinal node involvement, all with close proximity to the superior vena cava. Despite this being the leading cause, only 10% of small cell and 2% of non-small cell lung cancer patients will develop SVCS. Another malignant cause is lymphoma (7% of diffuse large cell lymphoma cases and 20% of lymphoblastic lymphomas). Metastatic cancers, including mesothelioma, breast, germ cell and thyroid cancers, account for about 5-10% of SVCS. Non-malignant causes comprise about 5% of cases, and include catheter-related thrombosis, tuberculosis, goiter, aortic aneurysm, histoplasmosis.

The superior vena cava (SVC) is formed by a merging of the brachiocephalic veins, which are in turn formed by the internal jugular and subclavian veins. Thus the SVC is the major venous drainage system for the head, neck, arms and upper thorax. In addition, the azygous vein empties into the SVC below the brachiocephalic veins. The actual location of the obstruction plays a role in the signs and symptoms, as an obstruction above the azygous vein allows for collateral circulation to develop more easily, possibly making symptoms less severe.

Clinical Presentation and Diagnosis

Symptoms may vary depending on the degree of obstruction, the development of collateral circulation (which, as mentioned before, depends on the location of the obstruction), and the underlying etiology. Typical symptoms include a feeling of fullness in the head, nasal stuffiness, headache, shortness of breath, cough, chest pain, hoarseness and difficulty swallowing. Physical signs may include dilated neck and/or chest veins, facial and/or periorbital edema, cyanosis and arm, breast, or upper chest swelling. Patients will usually report that symptoms are worse with certain positions, such as lying flat and bending over, or that they are worse upon waking in the morning (after lying down all night). Late signs and symptoms can include respiratory distress, headaches, syncope, visual changes, and mental status changes.

A chest x-ray is typically the first diagnostic study performed, which may detect a mass, pleural effusion, or mediastinal widening. A CT scan or MRI can determine the extent of a tumor or detect a thrombus in the superior vena cava. In some cases, sputum cytology may be beneficial in making a diagnosis. If at all possible, a biopsy should be obtained to determine the histology of the mass causing the SVCS. This diagnosis is necessary to plan treatment and treating the area with radiation before a diagnosis can make future histologic diagnosis difficult, if not impossible. In rare cases, a patient may present with significant respiratory compromise, requiring immediate treatment prior to determining the tumor type.

Treatment

Treatments for SVCS include radiation therapy, chemotherapy, other pharmacologic therapy, and surgery. The treatment selection is dictated by the cause of the obstruction (type of tumor, presence of thrombus, etc.). Radiation therapy is the most commonly used treatment for SVCS, with 50-70% of patients having improvement in symptoms within two weeks. Interestingly, this is most likely not a result of the radiation, but rather the development of collateral circulation. Numerous radiologic (typically utilizing venogram) and post-mortem studies found that SVC patency was rarely achieved with radiation, despite improvement of symptoms. Studies in dogs have shown that relief of symptoms coincided with rapid development of collateral circulation (within 7 days), and that acute occlusion of the SVC was rarely fatal. Therefore, these findings do not support a need for emergent radiation therapy in patients with SVCS. Side effects of radiation will vary depending on the areas included in the treatment field, and can include: skin irritation, dyspnea, cough, pneumonitis, mucositis, decrease in blood counts, appetite / taste changes, and fatigue.

Chemotherapy alone can be an effective treatment of SVCS caused by chemotherapy-sensitive tumors, such as lymphomas or small cell lung cancers, and may be used in combination with radiotherapy in other types of cancer. In addition, chemotherapy may be used alone if the patient has previously received radiation to the mediastinal field. Chemotherapy regimens are based on the tumor type, and side effects will depend on the medications used.

Other medications used in the treatment of SVCS include corticosteroids, diuretics, and thrombolytic therapy. The use of corticosteroids is thought to decrease tumor swelling and, in turn, decrease pressure on the SVC. Although they are commonly used, their efficacy has not yet been proven in studies. If utilized, high doses of corticosteroids should be limited to short periods of time. Diuretics are thought to decrease venous blood flow, therefore decreasing pressure in the SVC. These should be used with caution, as they may lead to hypovolemic shock due to low venous return to the heart. Thrombolytic therapy should be used when the SVCS is a result of a catheter-induced thrombus. This therapy may include heparin, warfarin, and/or tissue plasminogen activators. Due to the risk of bleeding, particularly in patients receiving other cancer therapy, the risks and benefits of this therapy make it a patient specific decision. Depending on the extent of the clot, removal of the catheter may be necessary.

In certain cases, stent placement may be an option for treatment. Stents can be placed percutaneously, do not typically require general anesthesia, and result in symptom relief in 75-90% of patients within 48 hours. This therapy clearly provides the quickest relief of symptoms, but is not available in all institutions. Obviously, the stented patient will still require therapy to treat the underlying malignancy. These patients will also require some type of anti-coagulant or anti-platelet therapy for life in order to maintain patency of the stent, which may or may not be problematic for future therapy. In addition, the available stents are metallic, so these patients will not be able to have MRI scans as follow up for future therapy. Other surgery is typically reserved for non-malignant causes of SVCS.

Treatment for non-malignant causes of SVCS will be directed toward the cause of the obstruction, but will not be discussed in this article. Treatment selection for SVCS caused by malignancy is patient specific, determined by tumor type, symptoms, future therapy needs, and the patient's baseline health.

Nursing Interventions

Nurses are in a key position to recognize SVCS early, allowing time for a clear histologic diagnosis prior to starting therapy. Nurses should be able to recognize those patients at high risk and be aware of the signs and symptoms of SVCS. Nursing care encompasses a variety of tasks: facilitation and coordination of diagnostic procedures, assessment of respiratory, cardiac and neurologic systems, administration of ordered therapies, emotional and psychosocial support for the patient and family, and education regarding treatment. Nurses can institute measures to help relieve dyspnea, including elevating the head of the bed, administering oxygen, and teaching energy conservation. Intravenous fluids should not be given through the upper extremities, necessitating central venous access. Additional nursing interventions should focus on the side effects caused by the treatment used (chemotherapy, radiation therapy). Through astute observation and an understanding of this complication, nurses can be instrumental in the diagnosis and treatment of SVCS.